Field of Invention
The present invention relates to a camera module, and more particularly to a portable camera module incorporated in a mobile phone, a notebook computer, a tablet computer or the like, and also particularly to a method of manufacturing the camera module.
Description of Related Arts
Nowadays, with the miniaturization and flatness development of portable electronic devices such as mobile phones, tablet PCs, notebook computers and so on, all component installations thereof are required to be thinner and smaller. The camera, which is one of the common components normally equipped in the above electronic devices, is also required to be smaller and thinner. The camera module as the core component of the camera is also required to be thinner and smaller.
Currently, the camera module in many mobile phones has a thin metal sheet which is called a substrate by those skilled in the art. The thin metal sheet applying on the camera module in the mobile phone is first invented by the inventor of the present invention. The thin metal sheet applying on the camera module of the mobile phone has been widely used in the art, but few people can deeply understand its principles.
Why is a substrate required in camera module? The main reason is that a photosensitive unit of the camera module has evolved into an electronic photosensitive unit (the electronic photosensitive unit is commonly known as “chip” mainly including the CCD and the CMOS, the photosensitive unit converts the optical signals into electrical signals, and a circuit board transmits the electrical signals to a phone's CPU for signal processing, and then the electrical signals is converted into images on a phone screen which human eyes can identify). Since the photosensitive unit is a light sensing unit, the photosensitive unit must be aligned with the position of an optical lens and try not to be deflected. It is worth mentioning that the photosensitive unit is contacted to the circuit board. Since the circuit board is not flat and is easily deformed after heated, it will affect the photosensitive unit contacted on the circuit board, resulting in a deflection of the photosensitive unit relative to the optical lens. A flat member which has a rigid and large surface is needed to control the deformation of the circuit board. In addition, the metal made flat member has a good heat-conducting property. As a result, the metal sheet-shaped substrate is used in the camera module.
However, with the higher demands on the phone cameras, the cameras not only require good imaging quality but also configures to be lighter and thinner, so the photosensitive unit must be constantly improved to have better performance. However, during a process of photoelectric conversion, the photosensitive unit will generate a relatively large amount of heat, resulting in deformation in the internal of the circuit board when the lens is used for a long time. A conventional camera module as an example is illustrated as follows.
As shown in FIG. 1 of the drawings, the conventional camera module generally comprises a base 10′, an optical lens unit 20′ provided on the base 10′, a substrate 30′ provided under the base 10′, a circuit board 40′ provided on the substrate 30′ and a photoelectric conversion element 50′ provided on the circuit board 40′ and under the optical lens unit 20′. Typically, the photoelectric conversion element 50′ includes a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor). The circuit board 40′ is a flexible board or a rigid-flex circuit board.
As shown in the drawings, the circuit board 40′ is overlapped on the substrate 30′. The photoelectric conversion element 50′ is further overlapped on the circuit board 40′. In this way, there are the following problems. Firstly, as the circuit board 40′ is generally not very flat, the photoelectric conversion element 50′ is difficult to flatly overlap on the circuit board 40′, thus the position of the photoelectric conversion element 50′ will be deflected relative to the optical lens unit 20′ and the imaging results quality will be affected. Secondly, the photoelectric conversion element 50′ generates a huge amount of heat during operation, as the photoelectric conversion element 50′ is located on the circuit board 40′. The heat is not easy to be dissipated to outside by the circuit board 40′ and the circuit board 40′ will be deformed after heated. The photoelectric conversion element 50′ is further defected in relative to the optical lens unit 20′ resulting in affection of the imaging results quality. If excessive heat is generated, the circuit board 40′ may even be burned. Thirdly, as shown in FIG. 2 of the drawings, the photoelectric conversion element 50′ is affixed to the circuit board 40′ by glue and a thinker glue-layer is needed to be coated to overcome the non-flatten surface of the circuit board 40′. In other words, only the bulging portion of the circuit board 40′ is contacted with the surface of the photoelectric conversion element 50′, such that the circuit board 40′ cannot securely couple to the photoelectric conversion element 50′. In order to firmly connect the surface of the circuit board 40′ with the photoelectric conversion element 50′, a thick glue-layer is filled at the gap between the circuit board 40′ with the photoelectric conversion element 50′. Although the non-flatten problem between the circuit board 40′ and the photoelectric conversion element 50′ is solved, the glue-layer causes another problem. The thickness of the glue-layer increases a thickness of the overall camera module. Fourthly, normally the substrate 30′ is made by a sheet-shaped element having a certain rigidity and a good heat-conductive performance, such that the circuit board 40′ and the photoelectric conversion element 50′ will have a flat surface corresponding. In addition, the heat emitted from the photoelectric conversion element 50′ can be dissipated outside by the substrate 30′. However, as the circuit board 40′ is provided between the photoelectric conversion element 50′ and the substrate 30′, the heat-conductive performance is limited. More seriously is that as the substrate 30′, the circuit board 40′ and the photoelectric conversion element 50′ are connected to form a five-layer structure with two glue-layers. As a result, the heat-conductive performance of the substrate 30′ is further limited.